Thermosetting resin decorative plates are excellent in various properties such as impact resistance, stain resistance and pencil hardness. Specific examples of the thermosetting resin decorative plates include high-pressure melamine resin decorative plates, low-pressure melamine decorative plates, diallyl phthalate (DAP) resin decorative plates, polyester decorative plates, guanamine resin decorative plates and phenol resin decorative plates. Among these decorative plates, in particular, the high-pressure melamine resin decorative plates have been extensively used for tabletops, sinks, top plates for desks, etc., because they exhibit a high surface hardness, are excellent in heat resistance and stain resistance, and have a good design property capable of allowing various color patterns to be selectively used therefor.
The high-pressure melamine resin decorative plates have been generally produced by the following method. That is, a melamine resin is impregnated into a decorative paper provided on a surface thereof with printed patterns. Then, an overlay paper impregnated with a melamine resin is superposed on a surface of the decorative paper, and a core paper prepared by impregnating a thermosetting resin such as a phenol resin into a paper substrate such as a kraft paper, is superposed on a back surface thereof. The resultant layered structure is sandwiched between metal plates and molded into an integral laminate by applying a high temperature and a high pressure thereto.
However, the production efficiency of these conventional melamine resin decorative plates is low because of complicated production process thereof. To solve this problem, there have been proposed melamine resin decorative plates which are produced without conducting the above resin impregnating step, i.e., by superposing an overlay paper on a surface of a resin-non-impregnated decorative paper and a core layer on a back surface thereof, and then forming the resultant layered structure into an integral laminate by applying a temperature and a pressure thereto (refer to JP 48-5866A and JP 52-100576A). In the above conventional method, the melamine resin impregnated into the overlay paper is fluidized by heating, and a part of the fluidized melamine resin is penetrated into the decorative paper. When the resin is thermally cured, the respective layers are integrated into a late to produce the melamine resin decorative plates.
However, the above melamine resin decorative plates have such a problem that the printed patterns provided on the surface of the decorative paper are concealed by the overlay paper, resulting in poor design property of the obtained decorative plates. To solve this problem, there has been proposed such a melamine decorative plate which is produced by successively laminating a melamine resin-impregnated paper and a core layer on a resin-non-impregnated back surface of a decorative paper and then forming the laminated structure into an integral laminate by applying a temperature and a pressure thereto (refer to JP 10-95091A).